This invention relates to an apparatus for separating a filtrate and a concentrate of solids from a solids-containing fluid. More particularly, this invention relates to a dynamic concentrator having a rotor therein.
Various types of dynamic filtration devices have heretofore been known for concentrating the solids content of a fluid. For example, as described in U.S. Pat. No. 3,437,208, dynamic filters have been known with a number of stationary circular filtering members of hollow construction which are disposed between a number of rotating bodies which facilitate movement of a solids-containing fluid through and into the filtering member. During operation of such devices, a solids-containing fluid is pumped under pressure across the surfaces of filtering screens or diaphragms of the assembled filter members so that a portion of the fluid is passed through the diaphragms and into the supporting filter member structures. Such fluid is thereafter removed as a filtrate. At the same time, with a filtration device of the type described in U.S. Pat. No. 3,437,208, solids tending to remain on the filtering diaphragms during the filtering operation are continuously returned into the solids-containing fluid to increase the concentration of solids within the filtration device and thereby form a thickened slurry for subsequent removal from the device.
Provisions have also heretofore been made for cleaning the surfaces of filtering diaphragms to remove any accumulation of solids material thereon. In some instances, the filtration devices have been periodically dismantled in order to remove the filtering diaphragm for cleaning purposes. In other instances, a backwash arrangement has been used to wash solids from the filtering surfaces, for example by means of a flow of water from the interior of a hollow filter and into the device through the filtering diaphragms. In still other instances, vibrating plates have been used to produce a pressure wave for loosening solids accumulated on the filtering diaphragms, for example as described in U.S. Pat. No. 3,455,821.
Dynamic filters are also known in which filtering diaphragms are rotatable, such as in U.S. Pat. NO. 3,643,806. In these instances, scrapers have sometimes been positioned to extend across and be moved adjacent the surfaces of the filter diaphragms to scrape solids materials from the diaphragm surfaces and thereby clean the surfaces of the filter diaphragms.
In the case of a concentrator using stationary circular filters of hollow construction and rotor members therebetween, it has been found that there is a tendency for the centrifugal force generated in the solids-containing fluid by the rotor members to cause solids to collect in the concentrator in the regions radially outside of the rotor members, for example in the outer radial corners by adjacent filter members. It has also been found that there is a tendency due to a reduced rate of flow of the solids-containing fluid for solids to collect in the regions adjacent the hub or other means mounting the rotor member to the rotor shaft. It has been found that the tendency for accumulation of solids in the two mentioned regions occurs despite the use of scrapers for intermittently cleaning the surfaces of the filter screens or diaphragms. It has further been found that continued accumulations in these regions can impair the operation of the concentrator and also obstruct ready dismantling thereof, such as when it is desired to convert the concentrator to use with a different solids-containing fluid or hydraulically clean the unit between runs in order to obviate opening and mechanically cleaning the unit. Apart from any impairment of efficiency during operation of the concentrator, a requirement for periodic halting of operation to clean out accumulated solids also impairs the overall efficiency of the concentrator by increasing its down-time.